1. The problem statement, all variables and given/known data A hollow box, mass M, rests on a frictionless surface. Inside the box is a spring, spring constant k, attached to one wall. A block, mass m, is pushed against the spring so that it is compressed an amount A. a. If after leaving the spring the block has velocity of magnitude v1, what will be the velocity of the box? b. The block slides across and hits the opposite side of the box. Assuming this collision to be perfectly elastic, find the velocities of the box and te block after the collision. c. What is v1? 2. Relevant equations p = mv m1*v1 + m2*v2 = m1*u1 + m2*u2 "u" is final velocity. 3. The attempt at a solution I'm lost. I know the spring is gonna exert a force on the box, so the box moves in the opposite direction. That's all I know.